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Principles of Economics 3e

19.3 Tracking Real GDP over Time

Principles of Economics 3e19.3 Tracking Real GDP over Time

Learning Objectives

By the end of this section, you will be able to:

  • Explain recessions, depressions, peaks, and troughs
  • Evaluate the importance of tracking real GDP over time

When news reports indicate that “the economy grew 1.2% in the first quarter,” the reports are referring to the percentage change in real GDP. By convention, governments report GDP growth at an annualized rate: Whatever the calculated growth in real GDP was for the quarter, we multiply it by four when it is reported as if the economy were growing at that rate for a full year.

This graph illustrates the change in real GDP over time. The y-axis measures real GDP in billions of 2009 dollars, in 2,000 dollar increments, from 0 to 20,000 dollars (20,000 billion is 20 trillion dollars). The x-axis shows years, from 1930 to 2020. In 1930, real GDP is roughly 1,000 billion dollars, or 1 trillion dollars. It rises over time to above 18,000 billion dollars, or 18 trillion dollars, in 2020.
Figure 19.10 U.S. GDP, 1930–2020 Real GDP in the United States in 2020 (in 2012 dollars) was about $18.4 trillion. After adjusting to remove the effects of inflation, this represents a roughly 20-fold increase in the economy’s production of goods and services since 1930. (Source:

Figure 19.10 shows the pattern of U.S. real GDP since 1930. Short term declines have regularly interrupted the generally upward long-term path of GDP. We call a significant decline in real GDP a recession. We call an especially lengthy and deep recession a depression. The severe drop in GDP that occurred during the 1930s Great Depression is clearly visible in the figure, as is the 2008–2009 Great Recession and the recession induced by COVID-19 in 2020.

Real GDP is important because it is highly correlated with other measures of economic activity, like employment and unemployment. When real GDP rises, so does employment.

The most significant human problem associated with recessions (and their larger, uglier cousins, depressions) is that a slowdown in production means that firms need to lay off or fire some of their workers. Losing a job imposes painful financial and personal costs on workers, and often on their extended families as well. In addition, even those who keep their jobs are likely to find that wage raises are scanty at best—or their employers may ask them to take pay cuts.

Table 19.7 lists the pattern of recessions and expansions in the U.S. economy since 1900. We call the highest point of the economy, before the recession begins, the peak. Conversely, the lowest point of a recession, before a recovery begins, is the trough. Thus, a recession lasts from peak to trough, and an economic upswing runs from trough to peak. We call the economy's movement from peak to trough and trough to peak the business cycle. It is intriguing to notice that the three longest trough-to-peak expansions of the twentieth century have happened since 1960. The most recent recession was caused by the COVID-19 pandemic. It started in February 2020 and ended formally in May 2020. This was the most severe recession since the 1930s Great Depression, but also the shortest. The previous recession, called the Great Recession, was also very severe and lasted about 18 months. The expansion starting in June 2009, the trough from the Great Recession, was the longest on record—ending 128 months with the pandemic-induced recession.

Trough Peak Months of Contraction Months of Expansion
December 1900 September 1902 18 21
August 1904 May 1907 23 33
June 1908 January 1910 13 19
January 1912 January 1913 24 12
December 1914 August 1918 23 44
March 1919 January 1920 7 10
July 1921 May 1923 18 22
July 1924 October 1926 14 27
November 1927 August 1929 23 21
March 1933 May 1937 43 50
June 1938 February 1945 13 80
October 1945 November 1948 8 37
October 1949 July 1953 11 45
May 1954 August 1957 10 39
April 1958 April 1960 8 24
February 1961 December 1969 10 106
November 1970 November 1973 11 36
March 1975 January 1980 16 58
July 1980 July 1981 6 12
November 1982 July 1990 16 92
March 1991 March 2001 8 120
November 2001 December 2007 8 73
January 2009 February 2020 2 128
April 2020 TBD TBD TBD
Table 19.7 U.S. Business Cycles since 1900 (Source:

A private think tank, the National Bureau of Economic Research (NBER), tracks business cycles for the U.S. economy. However, the effects of a severe recession often linger after the official ending date assigned by the NBER.

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